Niacin, a B vitamin, has long been used to increase high-density lipoprotein (HDL) cholesterol — the "good" cholesterol that helps remove low-density lipoprotein (LDL), the "bad" cholesterol from your bloodstream.

But niacin isn't for everyone. People who take niacin in addition to common cholesterol medications see very little additional benefit. And niacin can cause uncomfortable and sometimes dangerous side effects.

Niacin (nicotinic acid) is a B vitamin that's used by your body to turn food into energy. Niacin also helps keep your nervous system, digestive system and skin healthy. That's why niacin is often a part of a daily multivitamin, though most people get enough niacin from the food they eat.

When it's used as a treatment to increase your HDL cholesterol or correct a vitamin deficiency, niacin is sold in higher doses that are prescribed by your doctor. Prescription-strength niacin includes such drugs as Niacor and Niaspan.

Niacin is also available as an over-the-counter supplement. Supplements sold over-the-counter are not regulated like prescription medications. The ingredients, formulations and effects of over-the-counter niacin can vary widely.

Don't take niacin without discussing it with your doctor first because niacin can cause serious side effects when taken in high doses.

Niacin can raise HDL cholesterol by more than 30 percent. There's currently some debate about the exact role HDL plays in the body and in the development of heart disease. But HDL has generally been thought to pick up excess "bad" cholesterol in your blood and take it to your liver for disposal, which is why HDL is dubbed the "good" cholesterol.

Cholesterol levels are measured in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L):

In the past, it was thought that HDL levels would increase even more if niacin was added to cholesterol medications called statins, such as atorvastatin (Lipitor) and simvastatin (Zocor). But recent studies indicate that niacin provides little additional benefit when compared with statins alone, and may increase the risks of serious side effects.

Most doctors no longer recommend niacin for first line cholesterol control — except for people who can't tolerate statins. In those people, the benefits of niacin may outweigh the risk of potentially serious side effects.

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